1. Field of the Invention
The present invention relates to a cooling and guiding device used for manufacture of thermoplastic synthetic resin films by the inflation method or the T-die method, and particularly to a cooling and guiding device by which a thermoplastic synthetic resin film is passed continuously through a compartment formed by a plurality of conduit members with holes through them. The film is cooled by a coolant jetted out of many holes in the conduit members and while the film is cooled it runs along a specified route with a specified distance maintained between the conduit members and the film.
2. Description of the Prior Art
In the manufacture of flat films and bags made of thermoplastic synthetic resins (sometimes containing a filler material) such as polyethylene, polypropylene, etc., both the inflation method and the T-die method have been adopted for forming said flat films.
First, an outline of the inflation method will be presented in reference to FIG. 1. Thermoplastic synthetic resin pellets charged into an extrusion forming machine 12 through a hopper 10 are melted by heating in the machine 12 and the molten resin is put into a die 14. In this die the resin is blown by compressed air to become a cylindrical film or a blown film 16 which is commonly called a bubble. The outside of the bubble 16 is cooled by a cooling and guiding device 18. As it is cooled, it is guided along a specified route. After this the bubble 16 is squeezed by a stabilizing plate 20 and a nip roller 22 to become flat and finally it is rolled up by a take-up device (not shown) as a flat film or a flat bag.
In the manifold die method that is a representative arrangement of the T-die method, a wide pooling section (manifold) positioned perpendicular to the incoming resin from an extrusion forming machine is provided at the point where the resin enters a die. The resin that has been made wider by the manifold is extruded from the outlet (lip) of the die which has a thin linear opening. In the almost same way as in the inflation method the resin goes through a cooling and guiding device to become a flat film.
The reasons for employing the cooling and guiding device in the inflation method and T-die method are firstly to increase the forming speed for high production efficiency and secondly to improve such characteristics as transparency and strength of films, and thirdly to meet the requirement in the manufacture of the product so as to roll it up uniformly.
In the U.S. Pat. No. 4,453,907 for the invention for a cooling and guiding device with the inventor of the present invention, a conventional cooling and guiding device is disclosed in which an enveloping ring is formed by a combination of many conduit members, and cooling water is passed through those conduit members to cool the film which is going through the enveloping ring while the film is guided on a specified route.
However, since, with the conventional art, the film is cooled and guided in contact with the device (conduit members), it cools non-uniformly, and the thickness of the film varies. Since the film travels at a considerable speed sometimes the film is marred by contact with the conduit members. Furthermore, it is not practical to increase the speed of forming the film because of its contact with the conduit members.